PITTSBURGH — Players gathered their things in silence, while others hung their heads as they dressed. But in the midst of all the stillness, there was Brandon Marshall, delivering a saccharine sermon on the power of positivity.

Like a preacher behind the pulpit, Marshall cautioned against being discouraged by trials and tribulations. He spoke with overwhelming optimism, eschewing the stark realities of NFL history in favor of his faith — not only in himself but also in his downtrodden team.

For the third straight week, the Jets’ most glaring weaknesses — a sieve-like secondary, offensive struggles in the red zone, a nonexistent pass rush and questionable head-coaching decisions — were exposed and exploited Sunday. All of that culminated in a third straight defeat, a 31-13 loss to the Steelers.

Starting in 1990, only 6 percent of NFL teams have made the playoffs after beginning 1-4. But in the face of such unfavorable odds, Marshall remained upbeat.

“If you think it, it’ll happen,” the receiver said. “So I expect big things from this team. I expected them coming in, and just because we’re 1-4, I’m not going to give up. This is due season. I truly believe that.”

Their backs are “against the wall,” Marshall acknowledged. But the Jets have two choices, he said: They can “fold it up and cry” or they can stick together.

“Players, including myself, will get called out. And people will be asking to bench us. But this is perfect,” he added. “This is a perfect position for us. We have great talent in this room. We’re one of the most talented teams in the league.”

But all of that positivity can’t mask the truth: The Jets are not a good team. At least not yet.

Defensive breakdowns, dropped passes and blown assignments continue to be an issue. And their staff — notably Todd Bowles and offensive coordinator Chan Gailey — has been outcoached.

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The Jets had only one quarterback hit (Leonard Williams’ sack-fumble) on Ben Roethlisberger, who completed 34 of 47 passes for 380 yards and four touchdowns. Star wideout Antonio Brown had nine catches for 78 yards. Sammie Coates caught six passes for 139 yards, including a 72-yard touchdown on the Steelers’ opening drive.

“It [stinks] being 1-4,” said Bowles, who shouldered all of the blame for this loss. “ . . . As I lead, they follow. You can put it all on me.”

Trailing by 11 with 7:36 left in the fourth quarter, Bowles punted on fourth-and-2 at the Jets’ 46. Bowles said he hoped the Jets could force a three-and-out, but the Steelers (4-1) drove 79 yards for an insurance touchdown with 1:46 to play.

A third consecutive defeat might not even be the worst thing that happened to the Jets on Sunday. They began the day shorthanded, without injured starters Darrelle Revis (hamstring), Eric Decker (shoulder) and Brian Winters (concussion). By the end of the game, they were without inside linebacker David Harris (hamstring), center Nick Mangold (knee) and cornerback Darryl Roberts, who saw significant playing time because of Revis’ injury.

Across the room, however, there were no talking points of positivity or excited optimism. Instead, there were only clipped, monotone answers from defensive linemen Muhammad Wilkerson and Sheldon Richardson.